1. Field of the Invention
The present invention relates to an actuator device for use with an engine-idle control system of and automobile provided with an air-conditioner and, more particularly, to a vacuum controlled throttle positioning actuator having an improved mechanism for adjusting the stroke of operating plunger in association with throttle valve opening lever of an internal combustion engine.
2. Description of the Prior Art
In an automobile equipped with an air-conditioner compressor driven by internal combustion engine, it has been proposed that, under idling conditions of the engine, the opening degree of the throttle valve is slightly increased to provide the engine with a larger amount of air-fuel mixture when the air-conditioner compressor starts to run. It has been required to increase the engine power to prevent stalling of the engine under such loaded idling condition. A throttle valve operating mechanism of this general type includes a vacuum controlled throttle positioning actuator as found in U.S. Pat. No. 4,060,063 granted Nov. 29, 1977. Such conventional actuator does not include a mechanism for adjusting the stroke of operating plunger to maintain a predetermined increased opening degree of the throttle valve, so that it is difficult to reliably maintain a desirable opening degree of the throttle valve. On the other hand, actuators having an adjusting mechanism threaded through rear case portion of the actuator are shown, for example, in U.S. Pat. No. 4,137,876 granted on Feb. 6, 1979 and U.S. Pat. No. 3,547,088 granted on Dec. 15, 1970. Such conventional actuators are equipped with an adjustable stop for limiting stroke of the diaphragm. The adjustable stop is threaded through the housing of the vacuum chamber positioned behind the operating plunger, so that such stop is not applied to the actuator having a vacuum control such as solenoid valve provided in the vacuum chamber.
In a conventional actuator having an adjustable stop connected to the plunger, it has been proposed to use a double nut, however, it is difficult to adjustably move the double nut since such requires the use of two wrenches.